This invention relates in general to motor vehicle hydraulic systems. In particular, this invention relates to a damping element for integration into a hydraulic system, such as a motor vehicle hydraulic system.
Hydraulic systems are provided in various applications within a motor vehicle. Hydraulic brake and steering systems are two examples of such systems. These systems rely on hydraulic pressure, created by various sources, to effect their intended operation. Devices for autonomously generating brake pressure are part of driver assistance functions, such as, for example, a vehicle stability control (VSC). Autonomously generating brake pressure makes it possible to brake individual wheels or all wheels of the vehicle independently of the driver actuating the brake. Additional driver assistance functions may also include, for example, adaptive cruise control (ACC).
When the ACC function is activated, the distance and relative speed of a vehicle traveling up ahead is recorded, for example by laser distance sensors or radar distance sensors. The ACC function maintains a speed selected by the driver until a slower vehicle traveling up ahead is identified and a safe distance from it is no longer being maintained. In this case, the ACC function engages by braking to a limited extent and, if needed, by subsequent acceleration in order to maintain a defined spatial or temporal distance from the vehicle traveling up ahead. Additional ACC functions are expanded to the extent of also braking the vehicle to a stop. This is used for example in the case of a follow-to-stop function or a function to minimize the occurrence of a collision.
Further developments also permit a stop-and-go function, wherein the vehicle also starts automatically if the vehicle up ahead is set in motion again. The stop-and-go function typically executes a frequently changing autonomous pressure build-up to approximately 30 to 40 bar in the vehicle braking system independent of the generation of brake pressure originating from the driver. In the case of typical speeds on freeways, an autonomous deceleration is often restricted to approximately 0.2 g. At lower speeds, however, the system can generate an autonomous deceleration of 0.6 g, for example. A further development also includes an automatic emergency brake (AEB), whereby the AEB function detects potential accident situations in due time, warns the driver, and initiates measures to autonomously brake the vehicle with full force. In this case, rapid brake pressure build-up rates may occur.
An issue related to the operation of hydraulic systems, generally, is that hydraulic fluid pulsations may occur due to the operation of a hydraulic pump or for other reasons. These types of pulsations can lead to undesirable operating noises and can furthermore reduce the operating capacity of a hydraulic pump.
Thus, it would be desirable to provide an improved damping element or attenuator to dampen the low energy vibrations and pressure pulses. In particular, it would be beneficial to dampen these vibrations that occur on the inlet side of the pump during braking events, such as autonomous braking events.